Measuring operational and quality-adjusted efficiency of Chilean water companies

The path to a sustainable management of the urban water cycle requires the assessment of both operational and quality-adjusted efficiency in a unified manner. This can be done by the use of non-radial Data Envelopment Analysis models. This study used Range Adjusted Measure models to evaluate the operational, quality-adjusted, and operational & quality-adjusted efficiency (O&QAE) scores of the Chilean water industry including water leakage and unplanned interruptions as undesirable outputs. It was found that on average water utilities presented large O&QAE scores over time. The mean O&QAE score was 0.964 which means that water utilities could further reduce costs and undesirable outputs by 3.6% on average, while trying to expand the scale of operation. This finding suggests that excellent quality-adjusted efficiency at an efficient expenditure could be feasible. It was also evidenced that customer density, mixed water resources, and ownership influenced the O&QAE of Chilean water companies.

Climate change extreme and seasonal toxic metal occurrence in Romanian freshwaters in the last two decades—case study and critical review

The relationship between metal levels in the Olt River ecosystem in southern Romania (measured during 2018‒2019, with 1064 sediment and water samples) and daily climate data were explored to assess the need for targeted source identification and mitigation strategies. In 2018, there was a strong relationship between the sediment Pb, As, Cd, and Hg contents and temperature (r > 0.8, p < 0.001). Mercury in sediments had a positive correlation with precipitation, and Hg in the water correlated with minimum temperature in May 2018 (p < 0.01). In July 2019, heavy metals were positively correlated with precipitation and negatively correlated with temperature. According to nonsymmetrical correspondence analysis, the four climate parameters analyzed were linearly correlated with the frequency of metal detection (p < 0.001) in both years. The statistical analysis showed strong relationships between heavy metal levels and climatic factors and attributed the discrepancies in elemental concentrations between 2018 and 2019 to climate warming.

Forward osmosis (FO)-reverse osmosis (RO) hybrid process incorporated with hollow fiber FO

Currently, desalination is limited by high energy consumption and high operational and maintenance costs. In this study, a new concept of a hollow fiber forward osmosis (HFFO)-based infinity desalination process with minor environmental impacts (free-energy intake and no pretreatment or brine discharge) is suggested. To evaluate the concept, an element-scale HFFO was conducted in both conventional FO and pressure-assisted FO modes, simulating a submerged HFFO operation. In the HFFO test, the impacts of several operating conditions on the performance of the HFFO were investigated to select the best case. Based on these results, the energy costs were calculated and compared with those of a hybrid FO–seawater reverse osmosis (SWRO) process. The HFFO showed a high dilution rate of the draw solution (up to approximately 400%), allowing the downstream SWRO process to operate at 25 bar with the same permeate volume production (recovery rate of 60%). Consequently, the HFFO-based infinity desalination process has an annual energy revenue of 183.83 million USD, compared with a stand-alone two-stage RO process based on a 100,000 m3/day plant.

Modifying the resin type of hybrid anion exchange nanotechnology (HAIX-Nano) to improve its regeneration and phosphate recovery efficiency

In order to avoid eutrophication of freshwater systems, regulations all around the world have become increasingly stringent toward the maximum phosphate concentration allowed in wastewater discharges. Traditional phosphate removal methods such as chemical precipitation and enhanced biological phosphorus removal struggle to lower phosphate levels to the new requirements. Hybrid anion exchange nanotechnology (HAIX-Nano) is composed of a selective adsorption material able to remove phosphate down to levels close to zero. Moreover, HAIX-Nano is not affected by intermittent flow and does not produce sludge making it an interesting alternative. The regeneration process of HAIX-Nano typically requires a chemical solution with a high concentration of sodium hydroxide (NaOH) and sodium chloride (NaCl) (2–5% w/w of each). To lower the environmental impact and the operational cost of the technology, this study aims to enhance the HAIX-Nano regeneration efficiency. Therefore, the backbone of HAIX-Nano, which is normally a strong base anionic (SBA) resin, was changed for a weak base anionic (WBA) resin. The resulting material (WBA-2) exhibited a higher adsorption capacity than the traditional version of HAIX-Nano (SBA-1) under the tested conditions, while also showing a much higher regeneration efficiency. For a desorption solution of only 0.4% NaOH and no NaCl, WBA-2 showed an average regeneration efficiency of 78 ± 1% compared to SBA-1 with 24 ± 1%.

Water sources and kidney function: investigating chronic kidney disease of unknown etiology in a prospective study

A chronic Kidney Disease of unknown etiology (CKDu) has emerged with disproportionately high prevalence across dry lowland agricultural communities globally. Here we present the results of a prospective cohort of 293 patients with CKDu in the endemic region of Wilgamuwa, Sri Lanka, in whom we measured baseline kidney function and undertook quarterly follow up over 2 years. Well water was the primary historic drinking water source in the region, although a majority (68%) of participants reported switching to reverse osmosis water during study follow ups. Participants who reported ever drinking from well water had estimated glomerular filtration rates −6.7 (SD: 2.8) ml/min/1.73 m2 lower than participants who did not drink from well water historically (p = 0.0184) during the study period. Geospatial analysis identifies a cluster within the region where CKDu progression is significantly higher than the surrounding area. Samples of household wells (n = 262) indicated 68% had detectable agrochemical compounds with concentration above global water quality standards. It is expected that the detected contaminants compounds are indicators of poor water quality and that there is likely additional agrochemical exposure including commercial additives that may contribute to CKDu onset and/or progression. Thus, our study finds that well water exposure during a person’s lifetime in this region is associated with kidney function decline and identifies and quantifies putative nephrotoxic agrochemicals above safe drinking water concentrations in these wells.

The efficacy of chlorine-based disinfectants against planktonic and biofilm bacteria for decentralised point-of-use drinking water

Chlorine solutions are used extensively for the production of biologically safe drinking water. The capability of point-of-use [POU] drinking water treatment systems has gained interest in locations where centralised treatment systems and distribution networks are not practical. This study investigated the antimicrobial and anti-biofilm activity of three chlorine-based disinfectants (hypochlorite ions [OCl-], hypochlorous acid [HOCl] and electrochemically activated solutions [ECAS]) for use in POU drinking water applications. The relative antimicrobial activity was compared within bactericidal suspension assays (BS EN 1040 and BS EN 1276) using Escherichia coli. The anti-biofilm activity was compared utilising established sessile Pseudomonas aeruginosa within a Centre for Disease Control [CDC] biofilm reactor. HOCl exhibited the greatest antimicrobial activity against planktonic E. coli at >50 mg L−1 free chlorine, in the presence of organic loading (bovine serum albumen). However, ECAS exhibited significantly greater anti-biofilm activity compared to OCl- and HOCl against P. aeruginosa biofilms at ≥50 mg L−1 free chlorine. Based on this evidence disinfectants where HOCl is the dominant chlorine species (HOCl and ECAS) would be appropriate alternative chlorine-based disinfectants for POU drinking water applications.

The impact of on-premises piped water supply on fecal contamination pathways in rural Zambia

Reliable access to water, sanitation, and hygiene (WASH) services is a critical component of child health and development. However, as piped water systems with taps conveniently close to households are rare in rural, sub-Saharan Africa, there is limited evidence of their impact. We conducted a quasi-experimental study in four rural villages of southern Zambia between April 2018 and May 2019 in which we measured the impact of installing on-premises piped water systems on fecal contamination of stored water and caregivers’ hands. Gaining access to piped water was associated with a 0.5 log10 reduction of E. coli concentration in drinking water (p < 0.05) but no changes in hand contamination. The piped water systems in this study reduced the median distance to a safe drinking water source by over 90%, but we measured only small improvements in microbiological outcomes and no changes in the duration of self-reported, in-home water storage. These findings emphasize the need for future impact assessments of piped water systems to measure a comprehensive set of indicators directly linked to human well-being such as time savings.

Nanosilica modified with polyaspartic acid as an industrial circulating water scale inhibitor

Given the special performance of nanosilica with its small size, large specific surface area and high surface activity, nanosilica containing reactive amino group (denoted as SiO2–NH2) and polysuccinimide were allowed to take part in polymerization reaction to afford SiO2–NH2 modified polyaspartic acid (denoted as SiO2–NH2/PASP), a potential polymer scale inhibitor with good water solubility for industrial circulating water. The scale inhibition performance of the as-prepared SiO2–NH2/PASP was evaluated by static scale inhibition test; and its scale inhibition mechanism was explored by means of scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Results indicated that SiO2–NH2/PASP exhibits excellent scale inhibition performance against CaSO4 and CaCO3 at very low concentrations (optimum scale inhibition rate of 100% and 68%, respectively), and the presence of 5 mg/L of SiO2–NH2/PASP greatly increases the inhibition efficiency of CaSO4 and CaCO3 scale by 21% and 53%, obviously higher than that of pure PASP.